Solutions of lithium hexaflouroarsenate (LiAsF.sub.6) in dimethyl sulfite (DMSI) have found use as electrolyte in lithium cells and batteries. It is important that such electrolyte solutions possess good stability so as to be suitable for use as an electrolyte in lithium reserve cells requiring long term storage at temperatures ranging from -40.degree. F. to +165.degree. F., as required by U.S. Army military specifications. However, such solutions, when stored at elevated temperatures in sealed glass containers are unstable and deteriorate, as shown by the development of a bronzy discoloration and the generation of gaseous products, which can eventually lead to rupture of the container.